Examples of Complete Fertilizers

Compost can be a complete fertilizer if it has the right ingredients.

Fertilizers are classified by the ratio of nutrients included in the mix. A fertilizer must contain three key nutrients for it to be considered complete: nitrogen, phosphorous and potassium. Nitrogen helps keep plant leaves healthy, while phosphorous contributes to healthy root growth. Potassium helps flowering and fruiting plants and contributes to the immune system and overall health of the plant.

Commercial Fertilizer

Any commercial fertilizer with all three nutrients present is considered a complete fertilizer. A series of numbers indicates the nutrient mix in commercial fertilizers. The first number corresponds to the nitrogen content; the second number represents the phosphorous content; the third number represents the potassium content. So a fertilizer labeled as 10-5-5 is composed of 10 percent nitrogen, and 5 percent each of phosphorous and potassium. A 10-10-10 mix is just as much a complete fertilizer as a 10-5-10 mix. As long as there are no zeros present on the nutrient ratio label, the fertilizer is complete. Commercial fertilizers, whether liquid, solid or granular, have the nutrient contents somewhere on the label, making it easy to find out what you're feeding your plants.

Homemade Fertilizer

Homemade fertilizers are complete if they contain a source of nitrogen, a source of phosphorous and a source of potassium. The University of Alaska Fairbanks offers an example of complete homemade fertilizer made from fish waste, wood ash and animal bone ashes. The fish waste contributes nitrogen while the wood ash contributes potassium. The animal bone ashes contribute phosphorous. Each nutrient comes from an ingredient used to create homemade fertilizer; you'll get a rough idea of the nutrient content by how much of each ingredient you added to the mix. The downside to homemade fertilizers is that it's nearly impossible to tell exactly how much of each nutrient you're getting without having a sample tested by your local extension office or university laboratory.

Compost

Compost can be a complete fertilizer, depending what you add to your compost heap. Compost is a mixture of wet and dry ingredients, and most wet ingredients release nitrogen into the mix. Coffee grounds, yard waste and table scraps all contribute to the nitrogen content of compost. Some of these ingredients, like coffee grounds and leaves, also contribute to the potassium and phosphorous content of compost. As with homemade fertilizers, it can be hard to tell the exact nutrient composition of your compost without getting it tested, although knowing what and how much you put into your compost heap will give you a rough idea.

Manure

Manure describes animal fecal matter used for gardening purposes. Assuming the animal was fed a nutritionally sound diet, manure is a complete fertilizer in and of itself. Different types of manure have different nutrient contents. For example, horse manure has less phosphorous than manure from turkeys and chickens. Cow manure has more nitrogen than both horse and poultry manure. Again, local extension offices or university laboratories can sample the manure to give you an exact ratio of the nutrients in the fertilizer.